Numerical investigation of anchoring dynamics for stable attachment to rubble-pile asteroids

Anchoring mechanisms are essential for reliable attachment and stable operation of spacecraft on asteroid surfaces, where the combined effects of microgravity and unconsolidated regolith pose significant challenges. First, a biomimetic penetrating anchor for rubble-pile asteroid attachment is designed and introduced. Then, the anchoring process on discrete rubble-pile terrain is modeled and simulated via a proposed GPU-accelerated Discrete Element Method (DEM) framework. Within this framework, the complex interaction forces are computed based on the non-linear Hertz-Mindlin model, and a grid-based neighbor search algorithm is used to improve the computational efficiency. The simulation reproduces the complete anchoring sequence of the mechanism, namely penetration, claw deployment, and retraction. Simulation results suggest that the anchoring resistance exhibits a multi-peak characteristic during the deployment phase, which is driven by the sequential engagement of claw structures. Moreover, a comprehensive parametric study emphasizes the critical role of the microstructural state of the rubble-pile in anchoring performance. A competition between geometric matching and stochastic jamming is identified, that is, ordered packings provide high but fragile resistance for specific particle sizes ((Formula presented) ), while disorder enhances resistance for large particles ((Formula presented) ) through stable force arches. Furthermore, the anchoring capacity is demonstrated to be highly sensitive to the initial packing history of granular assemblies, with a sharp transition from solid-like interlocking to fluid-like slippage occurring as the initial lattice structure relaxes. The friction sensitivity analysis shows that sliding friction regulates the stability and probability of geometric self-locking, broadening the force distribution and promoting hyper-jamming events at high friction. Finally, stochastic analysis is performed, and it reveals that the anchoring forces follow a tri-modal, heavy-tailed distribution, spanning a wide range from approximately (Formula presented) (flow mode) to over (Formula presented) (hyper-jamming mode). The simulation results validate the proposed anchoring strategy and provide a fundamental basis for the future optimization of asteroid anchoring mechanisms.